Tau proteins are important in the assembly of microtubules. In normal brain, Tau is localized within the axons of the neurons, but in some neuropathological lesions it accumulates within the body of the neuron. Tau proteins are thought to be abnormally phosphorylated in certain disease states. Tau has been immunohistochemically localized to neurofibrillary tangles of Alzheimer’s disease (AD) brains. Tau proteins promote the assembly of tubulin monomers into microtubules and stabilize microtubules. Alternate splicing of Tau mRNA, glycosylation, and differential phosphorylation contribute to the heterogeneity of Tau.